This invention relates to a buoyant pipe system, in particular a submerged pipe system that is anchored to the floor of a water body and buoyed by a floatation chamber above the water body floor. The buoyant pipe system is designed in particular for the conveyance of wastewaters to an off-shore outfall point where the wastewaters are discharged for dispersion by ocean currents.
The problem of disposal of wastewaters has plagued many communities and has become a regional rather than community problem, particularly in coastal areas of large urban growth. When considered from a regional perspective, the volumes of wastewaters for treatment and disposal become remarkably large. With increasingly stringent anti-pollution requirements viable solutions become limited in number.
One solution, disposal at sea, is receiving renewed interest as the ecology of the sea becomes understood to a greater extent. While there may exist initial reservations about disposing of wastewaters often rich in organic materials and metal compositions of varying toxicity, the proposition requires careful consideration. As pointed out in the reasoned article, "The Disposal of Waste in the Ocean" by Bascom, Scientific America, Vol. 231, No. 2 (August 1974), in citing John Delsaacs of Scipps Institution of Oceanography, ". . . the sea is starved for the basic plant nutrients and it is a mystery to me why we should be concerned with their thoughtful introduction into coastal seas in any quantity that man can generate in the foreseeable future." It is pointed out in the article that marine life can not only tolerate, but can be enhanced by the introduction of certain wastes, that there are optimum levels of not only organic materials, but of metals such as zinc and copper generally considered toxic. Such materials, it is stated, must be presented to the ocean in the right places and at reasonable rates. Materials which should not be introduced to the ocean should be prevented entry at the source. Such source control is a consideration in every advanced regional planning system, whereby industrial discharges are required to have prior removal and alternate disposal of high toxics which are inadequately absorbed by the ocean ecology. Affirmative wastewater aquaculture is discussed in Marine Outfall Systems, Grace, sec. 3-9, (Prentice Hall 1978).
A substantial limiting factor in implementing a regional scale ocean outfall system is the massive investment in pipe and in the acquisition of on shore land for a pipe line right-of-way. Additionally, with regard to the terminal outfall, conventional outfall systems are difficult to maintain and subject to corrosion, sand abrasion and collapse from alluvial-type burial.
The pipe system proposed herein avoids the disadvantages of the conventional land collection and sea bed outfall systems. The system is similar in certain respects, but radically different in other respects from the prior art systems of Giraud et al, "Submarine Conveyance of Fluids Through a Flexible Pipe Line", U.S. Pat. No. 3,216,203, issued Nov. 9, 1965. It is proposed therein to suspend or anchor a buoyant pipe at the depth where the internal fluid pressure for transport of the gas or lighter than water liquid will equal the external water pressure, thereby allowing a flexible or thin wall pipe. It is proposed therein that weights or alternatively buoyant material be added to the pipe to properly achieve the equilibrium depth.
Unlike the system of Geraud et al, it is proposed herein that a pipe system be assembled which conveys wastewater to an outfall in which pressure is equalized by the admission of seawater wherein internal and external pressure are substantially equal regardless of depth. Furthermore, the pipe conduits forming the system are buoyed by a separate buoyancy chamber attached to the top of the conduit and are anchored in a submerged position above the floor of the water body. Prior to outfall the pipe system includes a plurality of submerged entry branches from multiple wastewater sources.
By maintaining a positive buoyancy to the pipe conduits, the system may follow the contour of the bed of the water body, or by use of varying length anchor cables follow a straight line or predetermined curve, or any combination of the aforementioned.